Five vulnerable pensioners were tied up like animals with sheets and their own braces at Northwick Park Hospital.
The restraint, which stripped them of their dignity, took place on Fletcher Ward between October and November last year.
A report published by Harrow Primary Care Trust (PCT), which ran the ward, said the unit was severely understaffed at that time.
Police were informed on November 12 when a patient was discovered tied to a chair with a bed sheet. Thirty four pensioners or their relatives were interviewed along with 33 members of staff.
It was later found the nurses on duty at the time did not have the required training. No arrests were made but the nursing staff involved were suspended.
An investigation carried out by Harrow PCT, responsible for the 26 bed ward, later identified four more OAPs who were inappropriately restrained.
In most cases they were tied to chairs using sheets, men's braces or wheelchair straps.
They were often left in that state for long periods of the day and night.
Rosanna Thurlow, spokeswoman from Action on Elder Abuse, was disgusted by the recent findings. She said: "Restraint is only ever appropriate as a last resort. I cannot see how the use of braces to restrain someone could ever be appropriate or a professional way to address the difficulty of a wondering patient. It is understandable that a human being might want to walk around now and again and to stop someone from doing this is a deprivation of their liberty.
"Inappropriate use of restraint is physical abuse and we must recognise it as such."
The PCT had been in financial trouble and there were insufficient levels of staff to cover the ward shifts. However, the number of admissions onto the ward continued to increase along with the level of patient dependency. There was also heavy reliance on 'bank' staff who did not have Protection of Vulnerable Adults (POVA) training.
Tony McNulty, Labour MP for Harrow East, said: "I have spoken to the PCT about this matter and we need to make sure this never happens again. The people from Harrow expect to receive dignified care from Northwick Park and staff need to be properly trained."
The report does not identify the members of staff who tied up the pensioners but says it is possible they intended to limit the risk of them falling. The management of the ward has now been taken over by North West London NHS Trust.
PCT Chief Executive Dr Sarah Crowther said: "As soon as we heard this allegation we set up our inquiry and interviewed staff on the ward as well as patients and their relatives.
"Whereas some form of restraint may be used by nursing staff with an elderly patient to protect him or her from harm, the examples we discovered were unacceptable. Internal disciplinary action has been taken and a programme of training has been introduced to ensure that all staff provide the best possible care for vulnerable patients."
In 2006 the PCT had identified the lack of staff as the biggest risk it faced but failed to make sure Fletcher ward was manned properly.